Hydrogen for Energy Storage Analysis Overview …. Scenarios for Hydrogen Energy Storage Analyses. National Renewable Energy Laboratory Innovation for Our Energy Future

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Hydrogen for Energy Storage Analysis Overview

National Hydrogen Association Conference & Expo

Darlene Steward, Todd Ramsden, Kevin Harrison

National Renewable Energy Laboratory

May 3-6, 2010

Long Beach, CA

NREL/PR-560-48360

This presentation does not contain any proprietary, confidential, or otherwise restricted information

2National Renewable Energy Laboratory Innovation for Our Energy Future

ObjectivesCompare hydrogen and competing technologies for utility-scale energy storage systems.

Explore the cost and GHG emissions impacts of interaction of hydrogen storage and variable renewable resources

OutlineStudy FrameworkPreliminary Study Results

– Lifecycle cost analysis for hydrogen and competing technologies

– GHG emissions credit impact for a remote wind farmNREL Wind to Hydrogen Study Perspectives

Hydrogen Energy Storage System Modeling

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Scenarios for Hydrogen Energy Storage Analyses

National Renewable Energy Laboratory Innovation for Our Energy Future3

BatteryElectricity

Pump/Compressor/Turbine

Electricity

Air or Water Reservoir

?Is hydrogen a potential solution for utility-scale energy storage

Shed electricity

?How would using hydrogen for storage impact cost and emissions for renewable resources Hydrogen

Storage

Shed electricity

Comparison of costs for hydrogen and competing technologies

Study of hydrogen energy storage for a specific renewable resource

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Energy Storage Scenario for Comparison Study

Nominal storage volume is 300 MWh (50 MW, 6 hours)o Electricity is produced from the storage system during 6 peak hours (1 to 7 pm)

on weekdayso Electricity is purchased during off-peak hours to charge the system

Electricity source: excess wind/off-peak grid electricity o Assumed steady and unlimited supply during off-peak hours (18 hours on

weekdays and 24 hours on weekends)o Assumed fixed purchase price of off-peak/renewable electricity

Source: HOMER model output

National Renewable Energy Laboratory Innovation for Our Energy Future

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Levelized Cost of Hydrogen and Competing Technologies

Hydrogen is competitive with batteries and could be competitive with CAESand pumped hydro in locations that are not favorable for these technologies.National Renewable Energy Laboratory Innovation for Our Energy Future5


Round-Trip Efficiency and Electricity Price Sensitivity

• Electricity price sensitivityo Low-capital-cost, high-efficiency pumped hydro system is sensitive to electricity priceo High-capital-cost NiCd system is insensitive to electricity priceo For other storage systems, sensitivity to electricity price is roughly inversely

proportional to round-trip efficiency

NiCd battery

CAES

FC abovegroundPumped hydro

FC/geologicH2 Comb turbine

NaS batteryVR battery

0.00%

2.00%

4.00%

6.00%

8.00%

10.00%

12.00%

14.00%

0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0%

Storage System Round-Trip Efficiency

Elec

trici

ty P

rice

Sens

itivi

ty (%

cha

nge

in

LCE/

c)



Energy Storage & Greenhouse Gases

Source: Denholm, Paul. (October 2006). “Creating Baseload Wind Power Systems Using Advanced Compressed Air Energy Storage Concepts.” Poster presented at the University of Colorado Energy Initiative/NREL Symposium. http://www.nrel.gov/docs/fy07osti/40674.pdf

+ -Additional energy from the windfarm can be captured for later use

Efficiency losses incurred by routing wind energy through the storage system reduce the greenhouse gas benefit of wind

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Wind Farm Location


The NREL Western Wind Data Set was used to identify a realistic

remote wind farm location

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Study Framework - Add Hydrogen Storage to a Base Case Without Storage


750 MW

Hydrogen Storage400 MT

Curtailed electricity

2%

Electricity to grid (storage + direct)87% of total wind farm output

Storage Constrained CaseElectricity to storage16% of total wind farm outputElectricity from storage5% of total output

500MW

Hydrogen Storage2,600 MT


12%

(storage + direct)68% of total wind farm output

Transmission Constrained Case

Electricity to storage27% of total wind farm outputElectricity from storage7% of total output


17%

Electricity to grid83%

750 MW

Base Case (without storage)


Analysis of the base case provides LCOE and avoided emissions for comparison


Primary Study Assumptions

Major Assumptionso Electrolyzer and PEM fuel cell

performance and cost values derived from mid-cost case of lifecycle cost analysis

o Hydrogen storage in geologic storage

o The storage system is located at the wind farm & all electricity charged to the storage system is derived from the wind farm

o A dedicated transmission line carries electricity from the wind farm/storage system to the grid near demand centers.

o Power from the wind farm will be curtailed (shed) if:

o It exceeds the maximum charging rate of the storage system + maximum capacity of the transmission line

o The storage system is full


Hydrogen Storage

Shed electricity

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Wind Farm and Hydrogen Storage for Storage Constrained Case - Hydrogen to Storage


0

5,000

10,000

15,000

20,000

25,000

30,000

1/2/0

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2/2/0

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Ener

gy (M

Wh/

day)

Electricity From Wind (kW)

Hydrogen to Storage (kW)


Wind Farm and Hydrogen Storage for Storage Constrained Case - Hydrogen from Storage


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5,000

10,000

15,000

20,000

25,000

30,000

1/2/0

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Ener

gy (M

Wh/

day)

Electricity FromWind (kW)Hydrogen fromStorage (kW)

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Summary of Preliminary Results


Storage reduces the amount of electricity that must be curtailed and reduces the LCOE

Base Case Storage Constrained

Transmission Constrained

Electricity Direct from Wind Farm to Transmission Line

82.7 82.7 60.8

Electricity from Storage N/A 4.5 7.4Electricity Shed 17.3 1.9 11.7Net Electricity to Transmission Line

82.7 87.2 68.2

Transmission Line Utilization 56.0 59.0 69.0

Without cost of carbon 13 10 12@ cost of carbon $50/MT CO2eq

9 6 8

@ cost of carbon $100/MT CO2eq

5 2 4

(% of Total Wind Farm Output)

(% of Total Transmission Line Capacity)

(LCOE ¢/kWh)


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Effect of a Cost of Carbon on the Competitiveness of Wind & Hydrogen Storage System

Cost comparison for Chicago Grid Electricity v Wind Electricity for Various Storage Configurations


0

2

4

6

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0 50 100

Cost

of

Elec

tric

ity

c/kW

h

Cost of Carbon $2008/MT CO2eq

Chicago grid

Base case wind

Transmission constrained wind

Storage constrained wind

Credit for avoided emissions reduces LCOE for wind electricity below grid price

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NREL Wind to Hydrogen Project - 10kW Wind Turbine Powered Electrolysis• Initial tests with third generation power electronics, wind speed

measurement and control algorithm indicate further improved energy capture of wind electricity into hydrogen production

0

2000

4000

6000

8000

10000

12000

14000

0 5 10 15 20 25 30 35 40

Wind Speed (MPH)

Pow

er (W

atts

)

Gen 2 – DC Power Gen 1 – DC Power

Planned increased energy capture from

Gen 2 to Gen 3

Increased energy capture from Gen 1

to Gen 2

Available wind power= Preliminary results

showing increased energy capture with new TSR algorithm. Algorithm is currently being tuned for stability.

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Cost Analysis

• Cost analysis performed based on NREL’s power electronics optimization and testing and on our electrolyzer cost analysis study

• Large centralized system capable of 50,000 kg per day production

• Optimized power conversion system due to a closer coupling of the wind turbine to the electrolyzer stack can reduce the total cost of hydrogen by 7%.

Capital Component (uninstalled) Baseline System

Optimized System

1.5 MW Wind Turbine

Rotor $248,000 $248,000

Drive Train $1,280,000 $1,180,000

including power electronics $100,000 $0

Control System $10,000 $10,000

Tower $184,000 $184,000

Balance of Station $262,000 $262,000

2.33 MW Electrolyzer $1,570,000 $1,350,000

including power electronics $220,000 $0

New Power Electronics Interface $0 $70,000

Resulting Hydrogen Cost ($/kg) $6.25 $5.83

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Key Findings from Wind2H2 RD&D

System Efficiency (HHV): At rated stack current…– The PEM electrolyzer system efficiency of 57% – The alkaline system had a system efficiency of 41%

• H2 production about 20% lower than the manufacturer’s rated flow rate• 50% system efficiency would be realized if rated flow were achieved

Cost Reductions from Power Electronics Optimization:– Analysis showed a potential 7% reduction in cost per kg of

hydrogen based on capital cost improvement• Projected cost of hydrogen falling to $5.83/kg from a baseline of

$6.25/kg

Energy Transfer Improvements: PV configuration testing compared direct-connection to the electrolyzer stack with a connection through power electronics– The MPPT power electronics system captured between 10% and

20% more energy than the direct-connect configuration


Thank You

Questions?

19

Thank You


Darlene [email protected]

Documents

Hydrogen for Energy Storage Analysis Overview …. Scenarios for Hydrogen Energy Storage Analyses. National Renewable Energy Laboratory Innovation for Our Energy Future